Iron deficiency anemia (IDA) is a major problem among adults and elderly. In men and postmenopausal women, IDA is currently thought to result from gastrointestinal (GI) blood loss. Despite thorough GI tract evaluation, a significant number of patients are found to be negative for fecal occult blood (FOB) and >30% do not have lesions consistent with chronic blood loss, suggesting that iron (Fe) malabsorption plays an important role. Currently, however, there is neither a suitable test to measure Fe absorption nor a role in the present scheme of GI examination for its evaluation. We propose to modify the current protocol for FOB testing to permit concurrent evaluation of both FOB and Fe absorption in a noninvasive test. The modification involves ingesting a gelatin capsule at bedtime that contains small quantities of Fe labeled with a non-radioactive (stable) isotope (Fe ), the recently developed nonabsorbable marker DyCl3, and the food colorant (visual stool marker) FD&C Blue No. 1.This is followed by laboratory analysis of a small sample of the visually marked stool for blood (the current practice) and the ratio Fe*/Dy; the latter provides accurate information on presence of iron malabsorption. During Phase-I, we will test the feasibility of this method by establishing the expectedly high value of iron absorption in healthy pre-menopausal women who are iron deficient without involvement of the GI tract. During Phase-II, we will evaluate the range of iron malabsorption that exists in IDA patients with suspected malabsorption (e.g celiac disease, H. pylori gastritis, or IDA patients refractory to iron supplementation, etc.) and in appropriate "controls" (IDA patients without malabsorption). During Phase-Ill, we will manufacture a "Test Kit', obtain FDA approval and work with the GI community to develop applications for measurement of iron malabsorption in the evaluation of IDA patients using private funds.